package contest1609;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

public class BXiaoMingRandomNumbers {
    static Scanner cin = new Scanner(new BufferedInputStream(System.in));//大量输入优化版本
    static PrintWriter cout = new PrintWriter(new BufferedOutputStream(System.out));//大量输出优化版本
    static PrintWriter cerr = new PrintWriter(System.err, true);//开启调试模式,一般输出量不大，不需要buffered

    public static void main(String[] args) {
        //TODO AOJ开启你的ACM传奇人生
        cerr.println("----Start your ACM legendary life with AOJ(www.webturing.com)----");
        int n = cin.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = cin.nextInt();
        }
        Arrays.sort(a);
        int[] b = new int[a.length];
        int m = 0;
        b[m++] = a[0];
        for (int i = 1; i < a.length; i++) {
            if (a[i] != a[i - 1]) {
                b[m++] = a[i];
            }
        }
        cout.println(m);
        for (int i = 0; i < m; i++) {
            cout.print(b[i] + " ");
        }
        cout.println();
        cin.close();//关闭输入流
        cout.close();//关闭输出流，这是必须的，否则一般不会自动刷新缓冲区


    }
}
